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US4975415A
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Cryochemical method of preparing ultrafine particles of high-purity superconducting oxides
Assignee: SRI International Inc
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Filing: 1987-07-10
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Granted: 1990-12-04
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Expires: 2007-07-10
Abstract
Abstract The present invention pertains to a method of preparing particles of superconducting ceramic powders, which method comprises: (a) dissolving the soluble salts of the cations in aqueous medium; (b) obtaining a solution having pH of between about 4 and 7 by optionally treating the aqueous medium with ammonia, or ammonium hydroxide; (c) atomizing the solution of step (b) onto liquid nitrogen at about -196° C.; (d) removing the liquid nitrogen by evaporation; (e) removing the water by sublimation at reduced pressure; (f) heating the solid residue of step (e) at 40-60° C. at reduced pressure; (g) calcining the solid residue in flowing oxygen or air at temperature of between about 200° to 895° C.; and (h) cooling the solid at a temperature of between about 900° C. and ambient temperature in sufficient air or oxygen and recovering the superconducting powder having an average diameter of between about 0.1 and 10 microns. Optionally, substep (h), additionally includes during cooling, the annealing of the particles in sufficient oxygen at between about 200° and 500° C. for between about 2 and 30 hrs. YBa 2 Cu 3 O 7-d (where d is 0-1) is preferred superconducting powder.
Inventors
- 👤 Michael I. Gusman
- 👤 Sylvia M. Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 12:28
CPC Classifications
C; C01; C01G; C01G3/00; C01G3/006; C01B; C01B13/00; C01B13/14; C01B13/18; C01P; C01P2004/00; C01P2004/01; C01P2004/03; C01P2004/60; C01P2004/61; C01P2006/00; C01P2006/40; Y; Y10; Y10S; Y10S505/00; Y10S505/725; Y10S505/73; Y10S505/737; Y10S505/738; Y10S505/742
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
208 words
An improved method of preparing fine particles of superconducting ceramic powders, which method comprises: (a) dissolving the soluble salts of cations in aqueous medium; (b) obtaining a substantially saturated solution of the salts and adjusting the pH to between about 4 and 7; (c) atomizing the solution of step (b) onto liquid nitrogen at about -196° C.; (d) removing the liquid nitrogen by evaporation of the nitrogen under reaction conditions such that the ice-salt crystals do not coalesce into larger particles; (e) removing the ice by sublimation at reduced pressure under reaction conditions such that the ice-salt crystals do not melt; (f) heating the solid residue of step (e) at about 40°-60° C. at reduced pressure under the reaction conditions such that the residue does not melt; (g) calcining the solid residue in sufficient oxygen or air at temperature of between about 200° and 895° C.; and (h) cooling slowly the solid at a temperature of between about 900° C. and ambient temperature in sufficient air or oxygen concurrently annealing the particles in flowing oxygen or air at between about 200° and 500° C. for between about 2 and 30 hrs and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 2
Dependent Claim
208 words
An improved method of preparing fine particles of superconducting ceramic powders, which method comprises: (a) dissolving the soluble salts of cations in aqueous medium; (b) obtaining a substantially saturated solution of the salts and adjusting the pH to between about 4 and 7; (c) atomizing the solution of step (b) onto liquid nitrogen at about -196° C.; (d) removing the liquid nitrogen by evaporation of the nitrogen under reaction conditions such that the ice-salt crystals do not coalesce into larger particles; (e) removing the ice by sublimation at reduced pressure under reaction conditions such that the ice-salt crystals do not melt; (f) heating the solid residue of step (e) at about 40°-60° C. at reduced pressure under the reaction conditions such that the residue does not melt; (g) calcining the solid residue in sufficient oxygen or air at temperature of between about 200° and 895° C.; and (h) cooling slowly the solid at a temperature of between about 900° C. and ambient temperature in sufficient air or oxygen concurrently annealing the particles in flowing oxygen or air at between about 200° and 500° C. for between about 2 and 30 hrs and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein in substep (b) the pH of about 4 to 7 of the aqueous solution is obtained by treating the aqueous medium with ammonia or ammonium hydroxide.
Claim 4
Dependent Claim
87 words
The method of claim 1 wherein the particles have a spinel or perovskite-like structure comprising: A.sub.x A'.sub.1-x B.sub.y B'.sub.2-y D.sub.z O.sub.q wherein: A and A' are each independently selected from lanthanum, yttrium, samarium, europium, gadolinium, dysprosium, holmium or mixtures thereof; B and B' are each independently selected from barium, strontium-calcium, barium-strontium or barium-calcium; D is selected from platinum, copper, silver, tin or mixtures thereof; x is about 1; y is about 2; z is about 3; and q is 7-d, where d is between 0 and 1.
Claim 5
Dependent Claim
17 words
The process of claim 1 wherein in step (b) the pH is between about 4 and 5.
Claim 6
Dependent Claim
19 words
The process of claim 1 wherein in step (a) the soluble salts are selected from organic and inorganic salts.
Claim 7
Dependent Claim
18 words
The method of claim 5 wherein in step (a) the soluble salts are selected from nitrates or acetates.
Claim 8
Dependent Claim
19 words
The process of claim 5 wherein the concentration of the soluble salts is between about 0.015 and 0.15 molal.
Claim 9
Dependent Claim
12 words
The process of claim 7 wherein A and A' are each yttrium.
Claim 10
Dependent Claim
9 words
The process of claim 8 wherein D is copper.
Claim 11
Dependent Claim
12 words
The process of claim 9 wherein B and B' are each barium.
Claim 12
Independent Claim
225 words
A method for producing particles of superconducting ceramic powders having a superconductivity transition temperature (T c ) of about 77K or greater, which method comprises: (A) dissolving the compatible soluble salts of the cations selected from nitrates or acetates in an aqueous medium; (B) obtaining a solution having a pH between about 4 and 7; (C) spray atomizing the solution of step (B) onto liquid nitrogen at about -196° C.; (D) removing the liquid nitrogen as a gas at about ambient temperature by evaporation without melting or coalescence of the ice-salt crystals; (E) removing the ice from the ice salt crystals by sublimation at reduced pressure without melting or coalescence of the ice-salt crystals into larger particles; (F) drying the salt crystals obtained in step (E) to about 40°-60° C. in a vacuum without melting or coalescence of the salt crystals; (G) calcining the solid residue of step (F) in sufficient oxygen or dry air at a temperature between about 200° and 895° C.; and (H) cooling slowly the solid of step (G) in an anhydrous atmosphere in sufficient oxygen or air to ambient temperature concurrently annealing the particles in sufficient oxygen or air at between about 200° and 700° C. for between about 2 and 30 hrs, and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 13
Independent Claim
225 words
A method for producing particles of superconducting ceramic powders having a superconductivity transition temperature (T c ) of about 77K or greater, which method comprises: (A) dissolving the compatible soluble salts of the cations selected from nitrates or acetates in an aqueous medium; (B) obtaining a solution having a pH between about 4 and 7; (C) spray atomizing the solution of step (B) onto liquid nitrogen at about -196° C.; (D) removing the liquid nitrogen as a gas at about ambient temperature by evaporation without melting or coalescence of the ice-salt crystals; (E) removing the ice from the ice salt crystals by sublimation at reduced pressure without melting or coalescence of the ice-salt crystals into larger particles; (F) drying the salt crystals obtained in step (E) to about 40°-60° C. in a vacuum without melting or coalescence of the salt crystals; (G) calcining the solid residue of step (F) in sufficient oxygen or dry air at a temperature between about 200° and 895° C.; and (H) cooling slowly the solid of step (G) in an anhydrous atmosphere in sufficient oxygen or air to ambient temperature concurrently annealing the particles in sufficient oxygen or air at between about 200° and 700° C. for between about 2 and 30 hrs, and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 14
Dependent Claim
24 words
The method of claim 11 wherein in step B the pH is obtained by contacting the aqueous medium with sufficient ammonia or ammonium hydroxide.
Claim 15
Dependent Claim
78 words
The process of claim 11 wherein the ceramic powder consists essentially of a ceramic oxide of the formula: A.sub.x B.sub.y D.sub.z O.sub.q wherein: A is selected from lanthanum, yttrium, samarium, europium, gadolinium, dysprosium, holmium, or mixtures thereof; B is selected from barium, strontium-calcium, barium-strontium, or barium-calcium; D is selected from copper, platinum, silver, tin, or mixtures thereof; x is about 1; y is about 2; z is about 3; and q is about 7-d, where d is 0-1.
Claim 16
Dependent Claim
22 words
The process of claim 11 wherein in step (A) the concentration of each soluble salt is between about 0.02 and 0.15 molal.
Claim 17
Dependent Claim
9 words
The process of claim 13 wherein A is yttrium.
Claim 18
Dependent Claim
9 words
The process of claim 15 wherein B is barium.
Claim 19
Dependent Claim
9 words
The process of claim 16 wherein C is copper.
Claim 20
Dependent Claim
23 words
The process of claim 11 wherein the ceramic particles of step (H) have an average diameter of between about 0.5 and 5 microns.
Claim 21
Dependent Claim
22 words
The process of claim 18 wherein the ceramic particles of step (H) have a diameter of between about 0.1 and 1.5 micron.
Claim 22
Independent Claim
209 words
A method of preparing particles of superconducting ceramic powders, which method comprises: (a) dissolving the soluble salts of the cations in two or more separate aqueous media; (b) obtaining separate cation solutions having pH of about 4 and 7; (b') mixing the separate solutions of steps (a) and (b) intimately for about 60 seconds then immediately; (c) atomizing the solution of step (b') onto liquid nitrogen at about -196° C.; (d) removing the liquid nitrogen by evaporation under conditions such that the ice-salt crystals do not coalesce into larger crystals; (e) removing the ice by sublimation at reduced pressure under reaction conditions such that the ice-salt crystals do not coalesce into larger particles; (f) heating the solid residue of crystals of step (e) to about 40°-60° C. at reduced pressure; (g) calcining the solid residue in sufficient oxygen or air at temperature of between about 200° and 895° C.; and (h) cooling the solid at a temperature of between about 900° C. and ambient temperature in sufficient air or oxygen concurrently annealing of the particles in sufficient oxygen at between about 200° and 500° C. for between about 2 and 30 hrs and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 23
Independent Claim
209 words
A method of preparing particles of superconducting ceramic powders, which method comprises: (a) dissolving the soluble salts of the cations in two or more separate aqueous media; (b) obtaining separate cation solutions having pH of about 4 and 7; (b') mixing the separate solutions of steps (a) and (b) intimately for about 60 seconds then immediately; (c) atomizing the solution of step (b') onto liquid nitrogen at about -196° C.; (d) removing the liquid nitrogen by evaporation under conditions such that the ice-salt crystals do not coalesce into larger crystals; (e) removing the ice by sublimation at reduced pressure under reaction conditions such that the ice-salt crystals do not coalesce into larger particles; (f) heating the solid residue of crystals of step (e) to about 40°-60° C. at reduced pressure; (g) calcining the solid residue in sufficient oxygen or air at temperature of between about 200° and 895° C.; and (h) cooling the solid at a temperature of between about 900° C. and ambient temperature in sufficient air or oxygen concurrently annealing of the particles in sufficient oxygen at between about 200° and 500° C. for between about 2 and 30 hrs and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.
Claim 24
Dependent Claim
23 words
The method of claim 20 wherein in substep (b) the pH is obtained by treating the aqueous medium with ammonia or ammonium hydroxide.
Claim 25
Dependent Claim
107 words
The method of claim 1 wherein the particles have a structure comprising: A.sub.j A'.sub.4-j B.sub.k B'.sub.4-k D.sub.m X.sub.n X'.sub.15-n wherein: A and A' are each cations independently selected from lanthanum, yttrium, samarium, europium, gadolinium, dysprosium, holmium or mixtures thereof; B and B' are each cations independently selected from barium, strontium-calcium, barium-strontium or barium-calcium; D is a cation selected from platinum, copper, silver, tin or mixtures thereof; X and X' are each independently selected from oxygen, fluorine or mixtures thereof; j is between about 0.7 and 4; k is between about 1.6 and 4; m is between about 2.6 and 6; and n is between 4 and 15.
Claim 26
Dependent Claim
17 words
The method of claim 22 wherein the particles after step (h) have a spinel or perovskite-like structure.
Claim 27
Dependent Claim
36 words
The method of claim 1 wherein in step (a) the cations are selected from metal cations, transition metal cations, rare earth cations or alkaline earth cations or mixtures thereof which are useful to produce superconducting materials.
Claim 28
Dependent Claim
13 words
The method of claim 24 wherein the cations are selected from metal cations.
Claim 29
Dependent Claim
16 words
The method of claim 1 wherein at least five cation solutions are mixed in substep (a).
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 7.5 Years (Year 8) | 1997-12-03 | 1998-06-04 | 1998-12-04 | $3760.00 | Window Closed / Lapsed |
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